Alylation product of 4(methylthio) phenol

ABSTRACT

Alkylthio substituted mononuclear phenolic age resistors and age resistant polymers containing said age resisters.

United States Patent Spacht Jan. 30, 1973 [54] ALYLATION PRODUCT OF [56]References Cited 4(METHYLTH1O) PHENOL UNITED sTATEs PATENTS [751 lnvenm"spach" Hudsm, 3,260,758 7/1966 O3Shea ..260 609 F [73] Assigneez TheGoodyear i & Rubber C 3,260,757 7/1966 OShea ..260/609 F FOREIGN PATENTSOR APPLICATIONS [22] Wed: 1970 812,530 4/1959 Great Britain ..260/609 F[21] App1.N0.: 64,641 1,117,110 5/1962 Germany ..260/609 F 1,116,6565/1962 Germany ..26/609 F RelatedUS. Application Data Division of Ser.No. 664,602, Aug. 31, 1967, Pat. No. 3,553,163.

U.S. Cl 260/609 F Int. Cl ..C07c 149/36 Field of Search ..260/60 QFPrimary Examiner-Elbert L. Roberts Assistant Examiner-D. R. PhillipsAtt0rneyF. W. Brunner and Vernon G. Parker [57] ABSTRACT 2 Claims, N0Drawings ALYLATION PRODUCT OF 4(METHYLTHIO) PHENOL This is a division ofapplication Ser. No. 664,602, filed Aug. 31, 1967, which issued Jan. 5,l971,as US. Pat. No. 3,553,163.

This invention relates to age resistors for oxidizable organicmaterials, their preparation and use in the stabilization of polymerswhich normally tend to deteriorate when exposed to normal atmosphericconditions and in particular when exposed to sunlight and/or elevatedtemperatures in the presence of air or oxygen.

Polymers have proven to be some of the most difficult organic materialsto successfully stabilize against the deleterious effects of oxygen andozone, particularly rubbery polymers, both natural and synthetic. Bothvulcanized and unvulcanized polymers are susceptible to the deleteriouseffects that are found in normal atmospheric conditions, and althoughmany materials have been suggested and used as polymer stabilizers nocompletely satisfactory material has been found that will fully protectthese polymers under the widely different conditions to which they aresubjected. The search for new and better polymer stabilizers such asphenolic stabilizers that are active and relatively nondiscoloring istherefore a problem which continues to command the attention of manyskilled investigators.

It is therefore an object of this invention to provide a new class ofphenolic antioxidants. Another object of this invention is to provide anew class of stabilizers for organic compounds that are relativelynondiscoloring.

In accordance with the present invention it has been found that theforegoing and additional objectives can be accomplished by employing asstabilizers for polymeric materials which are subject to the deleteriouseffects of oxygen, ozone and sunlight, phenolic compounds conforming tothe following structural formula:

wherein R is selected from the group consisting of hydrogen, alkylradicals containing one to 12 carbon atoms, cycloalkyl radicalscontaining five to nine carbon atoms, and aralkyl radicals containingseven to nine carbon atoms, R is selected from the group consisting ofalkyl radicals containing one to 12 carbon atoms, cycloalkyl radicalscontaining five to nine carbon atoms and aralkyl radicals containingseven to nine carbon atoms and R is a hydrocarbon radical containing oneto carbon atoms. Preferably R" is an alkyl radical containing one to 12carbon atoms.

Examples of specific compounds that conform to the above recitedstructural formula I are listed below:

2-tert. butyl-4-methylthio phenol 2,6-ditert. butyl-4-methylthio phenol2-benzyl-4-methylthio phenol 2-benzyl-4-ethylthio-6-tert. butyl phenol2-a-phenylethyl-4-propylthio phenol 6-tert. butyl-3-octylthio phenol6-cyclohexyl-3-methylthio phenol 2,4-ditert. butyl-S-dodecylthio phenol6-tert. octyl-3-methylthio phenol 2-tert. dodecyl-4-methylthio phenolThe aralkyl derivatives are particularly effective under conditionswherein the stabilized polymer or its vulcanizates are subjected toprolonged periods at high temperatures in the presence of air and/oroxygen.

Preferred compounds of the present invention are in particular thosewhich conform to the above structural formula I wherein R is selectedfrom the group consisting of hydrogen and alkyl radicals containing oneto 12 carbon atoms, R is a tertiary alkyl radical containing 4 to 12carbon atoms and R" is an alkyl radical selected from the groupconsisting of methyl, ethyl, propyl and isopropyl.

Specific examples of these preferred compounds are listed below:

3-methylthio-4-tert. butyl phenol 2-methylthio-5-tert. amyl phenol3-tert. butyl-4-ethylthio phenol 3-propylthio-4-tert. hexyl phenol6-tert. butyl-3-methylthio phenol 6-tert. amyl-2-ethylthio phenol2-methyl-4-methylthio-6-tert. butyl phenol 2,6-ditert.butyl-4-methylthio phenol 2-benzyl-4-methylthio-6-tert. butyl phenol4,6-ditert. butyl-3-methylthio phenol Even more preferred compounds arethose wherein R is attached to the phenolic nucleus in a position orthoto the hydroxyl group. Specific examples of these more preferredcompounds are listed below:

2-tert. butyl-4-methylthio phenol 6-tert. dodecyl-Zl-propylthio phenol4-methyl-2-propylthio-6-tert. butyl phenol The most preferred compoundsare:

6-tert. butyl-B-methylthio phenol 2-tert. butyl-4-methylthio phenol6-tert. butyl-Z-methylthio phenol One of the methods of preparing someof the compounds of this invention comprises reacting a mixturecomprising (A) at least one phenol conforming to the followingstructural formula:

R (II) wherein R is selected from the group consisting of hydrogen,alkyl radicals containing one to 12 carbon atoms, cycloalkyl radicalscontaining five to nine carbon atoms and aralkyl radicals containingseven to nine carbon atoms and R" is a hydrocarbon radical containingone to 20 carbon atoms and (B) at least one compound selected from thegroup consisting of olefins containing two to 12 carbon atoms,cycloolefms containing five to nine carbon atoms and arylalkenescontaining from seven to nine carbon atoms. Preferably R" is an alkylradical containing one to 12 carbon atoms. Component (B) is preferably atertiary olefin containing four to 12 carbon atoms.

An active halogen compound in some instances can also be used toalkylate the phenol. For example, a compound such as benzyl chloride canbe reacted with the phenol normally in the presence of a Friedel-Craftstype catalyst to provide an aralkyl substituent.

Examples of specific compounds that conform to the above recitedstructural formula (II) are listed below:

2-a-phenylethyl-4-methylthio phenol 4-benzyl-2-propylthio phenol'4-a-phenylethyl-2-propylthio phenol 3-benzyl-4-methylthio phenol6-dimethylbenzyl-3-hexylthio phenol 2-a-tolylethyl-4-butylthio phenol4-a-phenylethyl-3-ethylthio phenol 2-benzyl-4-dodecylthio phenolZ-methylthio phenol 3-ethylthio phenol 4-propylthio phenol2-ethyl4-methylthio phenol 4-propyl-2-methylthio phenol2-cyclohexyl-4-ethylthio phenol I Preferred phenolic reactants to beused in the previously described method are those conforming tostructural formula (II) above wherein R is selected from the groupconsisting of hydrogen and alkyl radicals containing one to 12 carbonatoms and R" is an alkyl radical selected from the group consisting ofmethyl, ethyl, propyl and isopropyl. Examples of these preferredphenolic reactants are listed below:

2methylthio phenol 3-methylthio phenol 4-methylthiophenol3-ethylthio-4-methyl phenol 3-propylthio-4-ethyl phenol2-ethylthio-5-propyl phenol 2-methyl-4-ethylthio phenol2-propyl-4-butylthio phenol Representative examples of the olefin typematerials that can be used in the above method are:

l-propene l-butene l-pentene Z-pentene 2-methyll -propene2-methyl-1-butene 2-methyl-2-butene 2-methyl-l -penteneZ-methyl-Z-pentene 3-methyl-2-pentene 2-methyl-1-hexene2-methyl-2-hexene 3-methyl-2-hexene 3-methyl-3-hexene I2,4,4-trimethyl-l-pentene cyclohexene styrene cyclopentene methylcyclohexene a-methyl styrene vinyl toluene methyl cyclopentene The mostpreferred olefins are tertiary olefins posessing 4 to 12 carbon atomssuch as some of those listed above.

In carrying out the previously described method a Friedel-Crafts typecatalyst, such as toluene sulfonic acid, anhydrous aluminum chloride,anhydrous ferric chloride and sulfuric acid can be used.

Solvents that may be used are selected from aromatic solvents such asbenzene, toluene, xylene and from aliphatic solvents such as hexane,heptane, gasoline, cyclohexane, etc.

Temperatures used for all processes are from 20 to 150 C. In general,reactions involving halides will be at higher temperatures than thoseinvolving alkylation with olefins, Preferred temperatures for reactionsinvolving elimination of hydrogen halide are from to C. Preferredtemperatures for alkylation reactions are from 60 to 100 C.

Molar ratios of reactants will depend primarily on the number of openpositions (ortho and para) on the alkylthio phenol. At least one mol ofalkylating agent (olefin, benzyl halide, etc.) should be used per mol ofalkylthio phenol. A slight excess 6f alkylating agent is preferred. Incase the alkylthio phenol has two reactive positions up to two mols ofalkylating agent may be used.

The following specific examples that show the preparation of compoundsconforming to the present invention are intended to be illustrative ofthe class of compounds disclosed and a method of their preparation butare not to be interpreted as limitations of the invention.

EXAMPLE 1 Seventy-seven grams of 4(methylthio)-meta-cresol, 100milliliters of benzene and 3.0 grams-of sulfuric acid were warmed to 50C. Fifty-two grams of styrene were then added over a 0.5 hour period.The mixture was then allowed to react overnight predominantly at roomtemperature. The catalyst was neutralized with aqueous sodium carbonateand the aqueous layer decanted. The mixture was heated under vacuum toremove volatiles. The yield was quantitative based on the materialscharged.

EXAMPLE 2 Seventy-seven grams of 4(methylthio)-meta-cresol, 64 grams ofbenzyl chloride and 0.5 gram of zinc chloride were mixed together andheated. All of the HCl resulting from the reaction was liberated after 5hours at a maximum temperature of 1 15 C. The mixture was heated to C.at 25 millimeters of mercury to remove volatiles. The yield wasquantitative based on a 1:1 molar ratio.

EXAMPLE 3 Seventy grams of 4(methylthio) phenol were dissolved in 100milliliters of toluene, to which was then added 4.0 grams ofconcentrated sulfuric acid. lsobutylene was added at a temperature ofabout 100 C. When the butylation was completed the catalyst wasdestroyed with aqueous sodium carbonate. After decantation of the waterlayer the residue was heated to 150 C. at 30 millimeters of mercury toremove the volatiles. The weight of product was 100 grams.

EXAMPLE 4 Seventy-seven grams of 4(methylthio)-meta-cresol, 100milliliters of toluene and 4.0 grams of concentrated sulfuric acid wereheated to 100 C. lsobutene was then added over a period of 3.5 hours.When butylation was completed the catalyst was destroyed with aqueoussodium carbonate. After decantation of the water layer the residue washeated to 150 C. at 30 millimeters of mercury to remove the volatiles.The weight of product was 97.0 grams.

somewhat on the nature of the polymer and the severity of thedeteriorating conditions to which the polymer is to be exposed. Inunsaturated polymers such as those made from conjugated dienes theamount of antioxidant necessary is greater than that required by asaturated polymer such as polyethylene. It has been found that aneffective antioxidant of the disclosed stabilizers in rubbery polymerswill generally range from 0.05 to 5.0 percent by weight based on theweight of the polymer although it is commonly preferred to use from 0.5to 2.0 percent by weight based on the weight of the polymer.

The polymers that may be conveniently protected by the phenoliccompounds in accordance with this invention are vulcanized andunvulcanized oxidizable rubber and those synthetic oxidizable polymerswhich are normally susceptible to deterioration by sunlight andatmospheric oxygen such as prepared from conjugated dienes as well asthe synthetic polymers and copolymers prepared from monoolefins.Representative examples of the synthetic polymers used in the practiceof this invention are. polychloroprene; homopolymers of a conjugated1,3-diene such as isoprene and butadiene and in particular,polyisoprenes and polybutadienes having essentially all of theirsegmeric units combined in a cis-l ,4 structure; copolymers of aconjugated 1,3-diene such as isoprene and butadiene with up to 50percent by weight of the polymer of at least one copolymerizable monomersuch as styrene and acrylonitrile; butyl rubber, which is apolymerization product of a major proportion of a monoolefin and minorproportion of a multiolefin such as butadiene or isoprene; and polymersand copolymers of monoolefins containing little or no unsaturation, suchas polyethylene, polypropylene, ethylene propylene copolymers andterpolymers of ethylene, propylene and a nonconjugated diene.

The practice of this invention is found particularly beneficial whenapplied to the stabilization of homopolymers of a conjugated 1,3-dienesuch as isoprene and butadiene and copolymers of said diene with up to50 percent by weight of at least one copolymerizable monomer such asstyrene and acrylonitrile. The practice of this invention is found mostbeneficial when applied to the stabilization of copolymers of butadieneand styrene. The method of addition of the stabilizers to the polymersis not critical. The stabilizers of the present invention may beincorporated into the polymers by any conventional means such as byadding to the polymer in latex form, to a solution of the polymer, tothe polymer on an open mill, by internal mixing, etc.

In order to evaluate the effectiveness of the compounds of thisinvention as stabilizers for polymers representative compounds of thisinvention were incorporated into an oxidizable polymer.

EXAMPLE 5 The products of Examples 3 and 4 (Experiments D and E) wereused to stabilize an extracted pale crepe natural rubber. One part ofeach product was added to a portion of the natural rubber on an openmill as part of the following formulation:

Ingredient Parts Extractedpale crepe 100.00 Zinc oxide 5.00 Sulfur 3.00Hexamethylenetetramine 1.00 Stearic acid 1.50 Antioxidant 1.00

The compounded rubber was then vulcanized, one portion for minutes at285 F. and another portion of minutes at 285 F. Each portion was thenaged in an oxygen bomb according to ASTMD-572. The percent tensileretention and weight increase after aging was taken as measures ofantioxidant efficiency. Other portions of the extracted pale crepe werestabilized and tested in the same manner with 1.0 part of 4(methylthio)phenol (Experiment B), a compound not within the scope of the presentinvention, and 4(methylthio)-m-cresol (Experiment C), a compound withinthe scope of the present invention. A control containing no' antioxidantwas also compounded, vulcanized, aged and tested. The data are listed inTable I.

Table I Tensile Retention Weight Increase Exp. Antioxidant 70/285 90/28570/285 90/285 A None 0 0 17+ 17+ B 4(methylthio) phenol 50.6 21.4 1.097.70 C 4(methylthio)- m-cresol 62.1 40.4 0.510 1.68 D butylated 4(methylthio) phenol (Ex. 3) 77.0 51.0 0.255 0.443 E butylated 4(methylthio) m-cresol (Ex. 4) 53.8 34.4 0.813 1.45

The above data reveal that materials within the practice of the presentinvention (Experiments C, D and E) afforded greater protection to thepale crepe than did the unsubstituted alkylthio phenol (Experiment B)and the unstabilized polymer (Experiment A).

EXAMPLE 6 Polypropylene (Profax 6501) was stabilized with 0.10 part of astabilizer within the scope of the present invention, the stabilizer ofExample 3 (Experiment H). Another portion of the polypropylene wasstabilized with 0.10 part of 2,6-ditertiary-butyl-p-cresol, a commercialantioxidant (Experiment G). The yield tensiles and melt indices of thesestabilized samples were compared with those of an unstabilizedpolypropylene control (Experiment F).

The polypropylene samples can be prepared in the following manner. Thestabilizer can be dissolved in acetone or hexane in a concentration of 1to 5 percent. The stabilizer solution can then be added to thepolypropylene (Pro-Fax 6501) by dispersing the stabilizer solutions inthe powdered polypropylene using a Henschel blender and agitating at2,800 rpm. After 15 minutes the typical batch temperature will normallyapproach 180 F. and a reasonable dispersion of the stabilizers will beobtained. After minutes only traces of the solvent will normally remain.

The stabilized'polypropylenes were injection molded to produce tensilebars, said tensile bars conforming to ASTM-D453 8-64 T. The tensile barswere aged at 140 C. in a forced air oven. The stress-strain propertiesof the original and aged samples were measured by an Instron. A 4% inchjaw was used, the jaw separation rate being 1 inch per minute.

Melt index determinations were made on the aged and unaged tensile barswhich had been cut up into small pieces. The melt index test was runaccording to ASTM D-l238-62 T, Condition L. As the polymer degrades themolecular weight is reduced by chain scission. The melt index indicatesthe molecular weight reduction and is expressed as grams of polymerextruded per unit time. As the molecular weight decreases due todegradation the melt index increases.

The test results appear in Table II.

" Expressed as grams of polymer extruded per 10 minutes.

The above results reveal the stabilization afforded polypropylene by thecompounds of the present invention. Whereas the yield tensile of theunstabilized polypropylene (Experiment F) dropped appreciably on aging,the yield tensile of the polypropylene stabilized commercial with acompound of the present invention (Experiment H) dropped more slowly andin fact was superior to the antioxidant (Experiment G) in this respect.7 H

The melt index on aging of the polypropylene stabilized with a compoundof the present invention (Experiment H) was superior on aging to boththe unstabilized polypropylene (Experiment F) and the polypropylenestabilized with the commercial antioxidant (Experiment G).

While certain representative embodiments and details have been shown forthe purpose of illustrating the invention it will be apparent to thoseskilled in this art that various changes and modifications may be madewithout departing from the spirit or scope of the invention.

What I claim is:

1. An alkylation reaction product prepared by alkylating4(methylthio)phenol with an olefin selected from the group consisting of2-methyl-1-propene 2-methyl-l-butene 2-methyl-2-buteneZ-methyl-l-pentene 2-methyl-2-pentene 3-methyl-2-pentene2-methyl-l-hexene 2-methyl-2-hexene 3-methyl-2-hexene 3-methyl-3-hexeneand 2,4,4-trimethyl-l-pentene, wherein the alkylation occurs at atemperature of from 20 C. to C. in the presence of a Friedel Crafts typecatalyst, at least one mol of olefin being charged per mol of4(methylthio) phenol.

2. The product of claim 1 wherein the olefin is 2- methyl- 1 -propene.

1. An alkylation reaction product prepared by alkylating4(methylthio)phenol with an olefin selected from the group consisting of2-methyl-1-propene 2-methyl-1-butene 2-methyl-2-butene2-methyl-1-pentene 2-methyl-2-pentene 3-methyl-2-pentene2-methyl-1-hexene 2-methyl-2-hexene'' 3-methyl-2-hexene3-methyl-3-hexene and 2,4,4-trimethyl-1-pentene, wherein the alkylationoccurs at a temperature of from 20* C. to 150* C. in the presence of aFriedel Crafts type catalyst, at least one mol of olefin being chargedper mol of 4(methylthio) phenol.